1. Field of the Invention
The present invention relates to a fuel supply control system for an internal combustion engine, and particularly relates to a system which corrects an operating characteristic of a fuel injection device that injects fuel into an intake pipe or a combustion chamber of the internal combustion engine.
2. Description of the Related Art
A fuel injection device generally includes an electromagnetic valve which opens for a time period based on a valve opening command signal supplied from a control device so as to inject fuel into an intake pipe or combustion chamber of an internal combustion engine. A relationship between the valve opening command signal and an amount of actually injected fuel changes depending on differences in the operating characteristic resulting from the manufacturing process or aging of the components. Accordingly, the amount of actually injected fuel occasionally shifts away from a target amount of fuel to be injected.
Japanese Patent Laid-open No. 2000-110647 (JP '647) discloses a method for calculating a deviation amount between the amount of fuel actually injected by the fuel injection device and the target fuel injection amount which is set according to the engine operating condition. The deviation amount is calculated based on an oxygen concentration detected by an oxygen concentration sensor disposed in the exhaust system of the engine and an intake air flow rate detected by an intake air flow rate sensor.
According to the method disclosed in JP '647, the deviation amount of the fuel injection amount is calculated as a simple scalar value. Accordingly, the deviation amount changes as the engine operating condition changes. Therefore, the method disclosed in JP '647 requires calculating a plurality of deviation amounts according to a corresponding plurality of engine operating regions.
Further, since the calculation of the above-described deviation amount is performed during a steady operating condition of the engine, it is necessary for the method of JP '647 to correct the fuel injection amount using the calculated deviation amount only within the steady operating condition in order to ensure sufficient correction accuracy.